Effects of intrinsic and atmospherically induced defects in narrow bandgap (FASnI3)x(MAPbI3)1−x perovskite films and solar cells
Abstract
Narrow bandgap mixed tin (Sn) + lead (Pb) perovskites are necessary for the bottom sub-cell absorber in high efficiency all-perovskite polycrystalline tandem solar cells. We report on the impact of mixed cation composition and atmospheric exposure of perovskite films on sub-gap absorption in films and performance of solar cells based on narrow bandgap mixed formamidinium (FA) + methylammonium (MA) and Sn + Pb halide perovskites, (FASnI3)x(MAPbI3)1−x. Structural and optical properties of 0.3 ≤ x ≤ 0.8 (FASnI3)x(MAPbI3)1−x perovskite thin film absorbers with bandgaps ranging from 1.25 eV (x = 0.6) to 1.34 eV (x = 0.3) are probed with and without atmospheric exposure. Urbach energy, which quantifies the amount of sub-gap absorption, is tracked for pristine perovskite films as a function of composition, with x = 0.6 and 0.3 demonstrating the lowest and highest Urbach energies of 23 meV and 36 meV, respectively. Films with x = 0.5 and 0.6 compositions show less degradation upon atmospheric exposure than higher or lower Sn-content films having greater sub-gap absorption. The corresponding solar cells based on the x = 0.6 absorber show the highest device performance. Despite having a low Urbach energy, higher Sn-content solar cells show reduced device performances as the amount of degradation via oxidation is the most substantial.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 10, 2020
- Source ID
- 10.1063/1.5126867
Entities
People
- Biwas Subedi
- Chongwen Li
- Maxwell M Junda
- Nikolas J. Podraza
- Yanfa Yan
- Zhaoning Song
Organizations
- Air Force Research Laboratory
- National Science Foundation
- Office of Naval Research
- Ohio Department of Development
- United States Department of Energy
- University of Toledo